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RE: 11th specimen of Archaeopteryx



  The real problem with the posture recovered for the *Mei long* holotype is 
that, regardless, it is not possible to discern "huddling" versus natural sleep 
posture. Suffocating animals take a variety of postures, and many of them mimic 
basal "fetal" positions of curling behavior, but that behavior is also one 
adopted during resting behavior. This is true of small cats and dogs found at 
Pompeii and Herculaneum, while suffocation behavior found in the Gobi can vary 
greatly so long as the burial regime differs (climbing behavior during burial 
in Djadokhta-level sediments). It's a tricky thing to simply say that the 
posture is necessarily one thing or another.

Cheers,

  Jaime A. Headden
  The Bite Stuff (site v2)
  http://qilong.wordpress.com/

"Innocent, unbiased observation is a myth." --- P.B. Medawar (1969)


"Ever since man first left his cave and met a stranger with a
different language and a new way of looking at things, the human race
has had a dream: to kill him, so we don't have to learn his language or
his new way of looking at things." --- Zapp Brannigan (Beast With a Billion 
Backs)


----------------------------------------
> Date: Mon, 31 Oct 2011 09:52:53 -0400
> From: jaseb@amnh.org
> To: martyniuk@gmail.com
> CC: dinosaur@usc.edu
> Subject: Re: 11th specimen of Archaeopteryx
>
> I have heard Paleontologists, including Chinese ones, suggesting that Mei did 
> roost on the ground just like geese do today. The idea that the type specimen 
> is displaying a roosting behavior (as opposed to an emergency sheltering 
> behavior) held in common with modern birds is also discussed in the monograph.
>
> This has been an excellent discussion of the enigmas of arboreality in 
> paravians. I would just add this.
>
> In discussing this we are discussing animals, perhaps one lineage of animals, 
> where evolutionary transitions were occurring (where one lineage gave rise to 
> proper birds). I am not an expert on evolutionary theory, but there must be a 
> state that sometimes occurs in evolutionary transitions where organisms have 
> not yet adapted anatomically to a new function or habitat, but are instead 
> adapting by sometimes straining to the maximum of their physical abilities. 
> This strain, in turn, provides the natural selection that leads to the 
> anatomical adaptation. In other words, some small paravian or basal bird was 
> in trees without a hallux, and this provided the selection pressure for a 
> hallux to evolve. It is the same with powered flight. There must have been 
> animals that were poor and tentative fliers, that lacked large sternal keels, 
> and in which the selection pressure for a large carina arose. Now, of course, 
> I know that this is adaptationism, and I am skeptical of strict 
> adaptationism, but there must be a subset of cases in evolutionary history 
> where features arose not sheerly through exaptation or evo devo consequences, 
> but through simple adaptation: If you have a slightly better grip on the 
> branch you are a little more likely to survive and leave offspring who also 
> survive.
>
> It may be impossible to prove definitively from fossil evidence, but the new, 
> small, Jurassic paravians may be just the creatures I'm referring to. Such a 
> hypothesis should be testable, though, by tracing the sequence of adaptations 
> across a better informed cladogram.
>
> There are also known cases where a group of animals perform a function which 
> is an important part of their biology and they simply never show an 
> anatomical adaptation to this function, it simply never arises. I now collect 
> photos of turkeys and other basal neornithines brooding their chicks in 
> trees. Looking at these images the parents certainly look awkward and we'd 
> all feel a lot more comfortable about the situation if they had feet like 
> Cracids. But they don't, they are somewhat ill suited to this sub-habitat, 
> and future Paleontologists will probably never ever be able to demonstrate 
> that they behaved this way.
>
> On Oct 31, 2011, at 8:19 AM, Matthew Martyniuk wrote:
>
> > For the record, I don't think anybody actually believes the _Mei_
> > specimen died while sleeping or resting normally, but rather was
> > probably sheltering itself against the volcanic ash cloud that buried
> > it. Whether or not this has any bearing on normal roosting behavior, I
> > don't know.
> >
> > Matt
> >
> > On Mon, Oct 31, 2011 at 1:32 AM, Don Ohmes <d_ohmes@yahoo.com> wrote:
> >> On 10/31/2011 1:10 AM, Tim Williams wrote:
> >>
> >>> I would have said roosting was related to locomotive activity, insofar
> >>> as the animal would be sitting, standing or perching on (or in) the
> >>> tree for long periods. That means that it has to adopt a stable
> >>> posture while sleeping or resting. There is no evidence in the
> >>> anatomies of_Archaeopteryx_ or any non-avian theropod that they were
> >>> capable of this. How did they prevent themselves from toppling off a
> >>> limb, when the manus and pes had minimal (if any) prehensile
> >>> abilities?
> >>
> >> Just guessing -- none of you guys have ever so much as climbed a tree?
> >>
> >>> Further, the 'tuck-in' sleeping posture adopted by_Mei_ seems
> >>> incompatible with roosting. Now, I'm not saying that all paravians
> >>> adopted this posture, or that those that did adopted it whenever they
> >>> slept or rested. But the fact remains that Archie and non-avian
> >>> paravians lack any adaptations for roosting, and at least one (_Mei_)
> >>> was preserved in a posture that showed it rested and slept on the
> >>> ground.
> >>
> >> Interesting. The part about Mei, that is... I will read up later.
> >>
> >>> Besides, I still don't see how tree-climbing qualified as a refuge for
> >>> small paravians, when so many potential predators were large - at
> >>> least as large as many tall trees.
> >>
> >> LOL. I really do not think the mega-theropods were targeting crow-sized
> >> animals, period. Or sticking their noses into thickety places. Even should
> >> that be the case -- hey, at least in a tree they would not get stepped on.
> >>
> >> Walking in the woods at night it is common to disturb roosting animals --
> >> they ALWAYS bail on the opposite side of the tree -- it is a very effective
> >> escape strategy.
> >>
> >> Good night, folks.
> >>
>
> Jason Brougham
> Senior Principal Preparator
> American Museum of Natural History
> jaseb@amnh.org
> (212) 496 3544
>
>